678 
POLLINATION OF FLOWERS 
The insect-pollinated flowers are usually 
bright-colored, often sweet-scented, and 
commonly yield nectar as well as pollen. 
The pollen, unlike the dry dusty pollen of 
wind flowers, is thickly beset Avith teeth, 
spines, knobs, pits, and grooves, which 
cause the grains to adhere together, and to 
the bodies of insects. Water is always 
hurtful to it, and there is an astonishing 
number of de\ T ices provided for its protec¬ 
tion, the mere description of which would 
fill many pages. It is probable that in¬ 
sects first visited flowers for the sake of the 
pollen, and that the function of secreting 
nectar was developed later. 
Any part of the flower may secrete nec¬ 
tar, as the bracts, sepals, petals, stamens, 
and pistils; but most frequently it is se¬ 
creted near the base of the styles. Its 
quantity varies from an almost impercep¬ 
tible layer to several drops or even a spoon¬ 
ful. In a tropical orchid Coryanthes there 
collects in the hollow lip over an ounce 
avoirdupois. 
Insects which are of importance as 
floAver-visitors belong to four orders: the 
beetles (Coleoptera) ;.the flies (Dipteral; 
the moths and butterflies (Lepidoptera), 
and the bees, Avasps, and their allies (Hy- 
menoptera). A few insects belonging to 
other orders occasionally are valuable as 
pollinators. Several species of bugs (Hem- 
ip tera) suck the nectar and are found on 
the flowers of the carrot, mustard, and aster 
families. A number of species of Neurop- 
tera visit the floAvers of the carrot family. 
The minute and active little insect knoAvn 
as Thrips is present in many flowers and 
sometimes effects pollination. It is very 
abundant on the flowers of the beet. 
Beetles and Floivers. —It would be much 
better for flowers if they were never visit¬ 
ed by beetles, for they cause more harm 
than benefit. As agents in pollination they 
are of little significance. The enormous dev¬ 
astation of foliage and bloom, the consump¬ 
tion and waste of pollen and nectar, the 
absence of hairs for holding pollen, and 
their indefinite manner of flight are factors 
Avhich greatly reduce their value as pollen- 
carriers. In New England 232 species of 
beetles belonging to 127 genera and 29 
families have been collected by Lovell and 
Frost on flowers. This is probably less 
than one-sixteenth of the total number of 
described species in this region. Why is 
it that so few feed on pollen and nectar? 
Their habits and forms in many instances 
answer this question; many are predaceous 
like the tiger beetles and ground beetles, or 
are scavengers; others are nocturnal or 
aquatic, or occur chiefly on the ground 
lurking beneath stones and boards, or liv¬ 
ing in the nests of other insects. 
Beetles are usually found on open flow¬ 
ers with the nectar visible or nearly visible, 
as the cherries, cornels, New Jersey tea, 
and goldenrods. On the flowers of the 
New Jersey tea ( Ceanothus americana ) 58 
different kinds have been collected. Most 
beetles feed upon both pollen and nectar 
and have been little modified in form as the 
result of their visits; but two remarkable 
genera, Gnathium and N emognatha, have 
acquired a slender suctorial tongue, like 
that of a butterfly, except that it cannot be 
coiled up. In one species it is nearly half 
an inch in length. Both genera live wholly 
on nectar, and thrust their tongues in and 
out tubular flowers with the precision and 
rapidity of bees. 
Many beetles pass their entire life on a 
single kind of plant. The blue flag beetles 
in the larval state feed on the seeds of the 
blue flag, and, in the adult form, live in the 
flowers. Many beetles are exceedingly de¬ 
structive to vegetation, as the rose chafer, 
the June bug, and the potato beetle. 
Fly-Flowers. —The flies are of far great¬ 
er importance as flower visitors than the 
beetles. Very many of the 8,000 North 
American species live largely or wholly on 
animal substances, but a large number also 
feed on pollen and nectar. The hover-flies 
(Syrphidae ) and the bee-flies visit floAvers 
which are similar to those attractive to 
bees; but for the more stupid flies there are 
pitfall-flowers, prison flowers, pinch-trap 
flowers, and flowers Avith deceptive nectar¬ 
ies, colors, and odors. 
Flowers with nauseous or indoloid odors, 
due to the decomposition of some nitro¬ 
genous compound, are attractive to flesh or 
carrion flies. The petals are often flesh- 
colored, blood-red, or dull dark purple 
marked with lurid stripes or spots. To some 
observers they suggest putrefying flesh or 
decaying carcasses; but in most instances 
